Yes. Muncie 4 speed
M21
Carb Sizing/vacuum or Mechanical
Moderator: Team
Re: Carb Sizing/vacuum or Mechanical
Some secondary diaphragm housings had a groove at the check ball, some not. Regardless , digging a deeper groove can work , but this is hard to measure and be consistent. Some had a bushing.
There is a better way. Installing a bushing with aprox .040” hole usually works good , no check ball used.
See picture below.
Another method ( Thanks to Tuner ) is to drill a bypass hole of .030” beside the check ball on an angle to the vacuum passage below. This hole can be enlarged if needed . If there is no slot it may require a .040” bypass. You retain the check ball.
On my my carb , I drilled the .030” bypass beside the check ball and used the standard plain spring.
No further adjustments were needed as the secondaries respond very well.
Also I have found the Quick fuel secondary pod 63-12QFT with the adjustment screw works very good. It has a .065” bushing and a purple spring .
There is a better way. Installing a bushing with aprox .040” hole usually works good , no check ball used.
See picture below.
Another method ( Thanks to Tuner ) is to drill a bypass hole of .030” beside the check ball on an angle to the vacuum passage below. This hole can be enlarged if needed . If there is no slot it may require a .040” bypass. You retain the check ball.
On my my carb , I drilled the .030” bypass beside the check ball and used the standard plain spring.
No further adjustments were needed as the secondaries respond very well.
Also I have found the Quick fuel secondary pod 63-12QFT with the adjustment screw works very good. It has a .065” bushing and a purple spring .
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Re: Carb Sizing/vacuum or Mechanical
I was adding the secondary signal tube (per Tuners posts) and noticed my new 3310 came with a bushing with a hole from Holley. I enlarged the hole and switched over to an adjustable lid from Allstate carb. Figured the needle would be the restriction regardless.
https://allcarbs.com/product/vacuum-sec ... djustable/
Seems to work good with a long yellow spring
https://allcarbs.com/product/vacuum-sec ... djustable/
Seems to work good with a long yellow spring
Re: Carb Sizing/vacuum or Mechanical
Holley 3310-1 original specs ( + or minus .001 )
Straight type squirter .025
Pump cam #218 White
Downleg boosters .140 with distribution tabs
PJ #72 SJ #76
Power valve PR 10.5 SEC 8.5
Primary metering block 5271 33101
PVRC .062
IFR .035 ( lower location )
Kill Bleed .028
Emulsion .028
Emulsion .028
Holes under mixture screws .060
Secondary metering block 7003 33101
PVRC .068
IFR .040 ( under brass plug top of block )
Emulsion .027
Emulsion .027
Main Body
PIAB .078
HSAB .027
SIAB .028
HSAB .026
Base plate
Secondary idle feed .024
Transition slot .220 x .023
Vacuum diaphragm Housing
Upper 34R-1334 B
Lower 79R-389B 4
.080 below check ball ( may not have a groove )
Check ball .187"
Plain spring
Straight type squirter .025
Pump cam #218 White
Downleg boosters .140 with distribution tabs
PJ #72 SJ #76
Power valve PR 10.5 SEC 8.5
Primary metering block 5271 33101
PVRC .062
IFR .035 ( lower location )
Kill Bleed .028
Emulsion .028
Emulsion .028
Holes under mixture screws .060
Secondary metering block 7003 33101
PVRC .068
IFR .040 ( under brass plug top of block )
Emulsion .027
Emulsion .027
Main Body
PIAB .078
HSAB .027
SIAB .028
HSAB .026
Base plate
Secondary idle feed .024
Transition slot .220 x .023
Vacuum diaphragm Housing
Upper 34R-1334 B
Lower 79R-389B 4
.080 below check ball ( may not have a groove )
Check ball .187"
Plain spring
Re: Carb Sizing/vacuum or Mechanical
The carb has all the correct parts. Body, baseplate, metering blocks etc. Pri and Sec jetting is even original spec of 72/76
Idle screws were 1 1/8
Transition slot was set large.
Both power valves have been changed to 6.5’s and the squirter is a 31 not a 25.
Vacuum secondary has no check ball and spring has no markings
Any starting suggestions for my engine as listed. Off to get some parts tomorrow. Carb is very clean…
Idle screws were 1 1/8
Transition slot was set large.
Both power valves have been changed to 6.5’s and the squirter is a 31 not a 25.
Vacuum secondary has no check ball and spring has no markings
Any starting suggestions for my engine as listed. Off to get some parts tomorrow. Carb is very clean…
Re: Carb Sizing/vacuum or Mechanical
Retro Roller 273/278 adv 223/225 @.050” 110 LSA installed at 105.5 ICL .544/.525 lift
MSD distributor. 18 initial 18 mech 36 total, 10 deg vac adv
Engine makes 14-15 in/hg at 800 RPM
I would start with a #70 PJ #76 SJ . Do you have an AFR gauge ?
6.5 power valves will be OK ,as that is what comes in most kits,
Dual power valves work good in a street car with limited traction. They transition AFR nicely.
With 14 – 15 inches of vacuum at 800 rpm idle , I think the .035 IFR will be OK to test. If this was an automatic in gear , the idle vacuum would drop to at least 12”
Your idle timing looks OK, although I wonder if 2-3 more degrees would help. You can test.
The squirter size at #31 is plenty large. I run the stock #25 with the #218 white cam on a 500 HP engine.
If you have a #25 or 28 I would try it. Not a tube type.
Set the secondaries to nearly closed , like about 1/2 turn.
Idle mixture screws set to 1.5 turns to start.
Can you see if the vacuum pod has a slot where the check ball goes. You may need a magnifying glass. This would be mandatory if you install the check ball. Your spring is probably the plain silver spring.
I can post the drilling of the bypass in the vacuum pod later if your interested.
MSD distributor. 18 initial 18 mech 36 total, 10 deg vac adv
Engine makes 14-15 in/hg at 800 RPM
I would start with a #70 PJ #76 SJ . Do you have an AFR gauge ?
6.5 power valves will be OK ,as that is what comes in most kits,
Dual power valves work good in a street car with limited traction. They transition AFR nicely.
With 14 – 15 inches of vacuum at 800 rpm idle , I think the .035 IFR will be OK to test. If this was an automatic in gear , the idle vacuum would drop to at least 12”
Your idle timing looks OK, although I wonder if 2-3 more degrees would help. You can test.
The squirter size at #31 is plenty large. I run the stock #25 with the #218 white cam on a 500 HP engine.
If you have a #25 or 28 I would try it. Not a tube type.
Set the secondaries to nearly closed , like about 1/2 turn.
Idle mixture screws set to 1.5 turns to start.
Can you see if the vacuum pod has a slot where the check ball goes. You may need a magnifying glass. This would be mandatory if you install the check ball. Your spring is probably the plain silver spring.
I can post the drilling of the bypass in the vacuum pod later if your interested.
Re: Carb Sizing/vacuum or Mechanical
Great info. Looking forward to the rebuild and the testing.
I do not have an AFR but plan on buying and installing one.
The vacuum pod does not appear to have a slot and no ball was installed.
Spring is silver with no markings
I do not have an AFR but plan on buying and installing one.
The vacuum pod does not appear to have a slot and no ball was installed.
Spring is silver with no markings
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Re: Carb Sizing/vacuum or Mechanical
Another question if I can…
The long tube that leaves the secondary on the passenger side??? I have not seen this befor. What is its purpose?
The long tube that leaves the secondary on the passenger side??? I have not seen this befor. What is its purpose?
Re: Carb Sizing/vacuum or Mechanical
Where's it ported to ? Think I've seen the one you mean, for oem replacement no doubt.
Ignorance leads to confidence more often than knowledge does.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Re: Carb Sizing/vacuum or Mechanical
Hot air choke supply. Supplies fresh air to tube in exhaust manifold that connects to choke housing. Just plug it.
Re: Carb Sizing/vacuum or Mechanical
The carb went back together very nicely. Ill being trying it out in the next couple weeks. I went with the 72/76 jetting to start. 28 squirter. 6.5/6.5 power valves. Long yellow spring and I added the quick change cover.
I have the transfer slots on the primary set square. Is this acceptable? Secondary was suggested at 1/2 turn. Is that a 1/2 turn off of fully seated?
I have the transfer slots on the primary set square. Is this acceptable? Secondary was suggested at 1/2 turn. Is that a 1/2 turn off of fully seated?
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Re: Carb Sizing/vacuum or Mechanical
Half turn from first contact of the screw. Just enough that the secondary blades don't stick in the bores. Yes primary transfer slots set square . Idle mixture screws set at 1.5 turns out for 2 corner idle carbs. ( 4 corner idle carbs are 3/4 turn ) Adjust when running.
Re: Carb Sizing/vacuum or Mechanical
I removed the 4776 600 Double Pumper and installed the 3310-1 780 Vacuum Secondary.
I only have 1/2 an hour of run time and some small adjustments made but so far I really like the carb. I cant explain why the idle is smoother but it is. As well I have yet to check if the secondary's are fully open but the carb feels even stronger above 3500 RPM than the 600 DP. I would say it is a touch weaker off idle and below 2500 RPM. That may be due to the carb spacer. The 600 was running with a fully divided plenum using a 3/8" gasket with four 1 5/8" holes matching the baseplate of the 600. I did not have a 4 hole gasket like this to match the 3310 baseplate so I used an open 3/8" gasket.
Carb idles great, has zero bogs anywhere, flat out pulls hard. I will play with the secondary's and do some jetting but as it sits, it will be staying on the Z28 Winters intake. Thanks to all for the advice...appreciate it!
I only have 1/2 an hour of run time and some small adjustments made but so far I really like the carb. I cant explain why the idle is smoother but it is. As well I have yet to check if the secondary's are fully open but the carb feels even stronger above 3500 RPM than the 600 DP. I would say it is a touch weaker off idle and below 2500 RPM. That may be due to the carb spacer. The 600 was running with a fully divided plenum using a 3/8" gasket with four 1 5/8" holes matching the baseplate of the 600. I did not have a 4 hole gasket like this to match the 3310 baseplate so I used an open 3/8" gasket.
Carb idles great, has zero bogs anywhere, flat out pulls hard. I will play with the secondary's and do some jetting but as it sits, it will be staying on the Z28 Winters intake. Thanks to all for the advice...appreciate it!